Residents in south suburban Park Forest are on alert after a man armed with a knife may have targeted as many as four teenaged girls.

Park Forest Police say the man they are after is likely involved in targeting four teenage girls. They say he may be familiar with the community, as all four crimes happened within a 1 mile radius, and he seems to strike during the daytime hours before and after school.

A Park Forest Police robo call went out to residents Wednesday night. Police say a student was headed to Forest Trail Middle School Wednesday morning when a masked man holding a knife approached her. It happened in the 300 block of Windsor Street. The girl ran away.

"It may be possible that he's aware now that we're looking for him. That said, a person wearing a ski mask out in public, especially as the weather is turning warmer, that should be a serious sign," said Deputy Chief Christopher Mannino, Park Forest Police Deparmtent.

Police are asking people to take a close look at this sketch. Investigators say this man may be responsible for targeting 4 teenage girls.

"That could easily be my son out there in the morning, walking to school or standing on the corner for the bus and that concerns me," said Arika Wesley.

"As a father, I have a 19-year-old and 6-year-old daughter. That is my worst fear, that something may happen to them and I'm not allowed to help defend them," said Donnie Woods.

On Monday, police say a man fondled a 15-year-old girl at this intersection near Sangamon and Shabbona. On March 18th, a 17-year-old girl was robbed at knifepoint and groped around Winnebago Park. Two days later, another 17-year-old was groped nearby.

So, when you add on the two cases this week, police offer this warning.

"Be alert, don't be looking down at a cell phone. Be aware of your surroundings. And, if possible, walk in groups," said Deputy Chief Mannino.

In the meantime, some residents are hopping in their vehicles and being pro-active.

"I have taken my fear and I have used it as a tool. I am out here to make sure that every last one of these kids get to where they have to go, get where they are going safely," said Tammy McDowell.

Police say one of the victims was one her phone when the man confronted her, and all the victims were alone at the time. Park Forest Police are asking residents to call if you see anything suspicious.